Method and apparatus for implementing operating changes and displaying operating change information for an implantable medical device

ABSTRACT

An implantable medical device, such as a pacemaker, stores information pertaining to a variety of events detected and/or triggered by the medical device for subsequent transmission to an external programmer device. The external programmer device displays graphical representations of the information under the control of a physician operating the programmer device. Examples of information stored by the pacemaker include information pertaining to operations triggered within the pacemaker as a result of the condition of the patient, such as an auto-mode switching event automatically triggered as a result of conditions detected within the heart, or as a result of the condition of the pacemaker itself, such as a battery test operation. Still other examples of information recorded by the pacemaker include information pertaining to programmer operations triggered by a remote programmer device, such as a heart base rate programming operation triggered by an external programmer.

This application is a divisional of application Ser. No. 08/995,783filed on Dec. 22, 1997, now U.S. Pat. No. 6,101,415.

FIELD OF THE INVENTION

The invention generally relates to implantable medical devices and toexternal programmer devices used in connection therewith and inparticular to methods and apparatus for processing information within anexternal programmer device pertaining to events recorded by theimplantable medical device.

BACKGROUND OF THE INVENTION

A wide range of implantable medical devices are provided for surgicalimplantation into humans or animals. One common example is the cardiacpacemaker. Another is the implantable cardioverter defibrillator. Otherexamples include devices for stimulating or sensing portions of thebrain, spinal cord, muscles, bones, nerves, glands or other body organsor tissues.

Implantable medical devices, particularly pacemakers, are oftenconfigured to be used in conjunction with an external programmer devicewhich allows a physician to program the operation of the pacemaker to,for example, control the specific parameters by which the pacemakerdetects arrhythmia conditions and responds thereto. For instance, theexternal programmer may allow the physician to specify the sensitivitywith which the pacemaker senses electrical signals within the heart andto further specify the amount of electrical energy to be employed forpacing the heart in circumstances where expected heart signals are notsensed. Additionally, the external programmer may be configured toreceive and display a wide variety of diagnostic information detected bythe pacemaker, such as the electrical heart signals sensed by thepacemaker and the responsive pacing signals.

With regards to the display of diagnostic information, many pacemakersoperate only in real time to detect electrical activity in the heart asit occurs and to transmit data pertinent thereto to the externalprogrammer for immediately display. In other words, no capability isprovided within the pacemaker for storing sensed signals for latertransmission to the external programmer. Hence, diagnostic informationcan only be retrieved and displayed for signals sensed by the pacemakerwhile the external programmer is currently communicating with thepacemaker, which is typically only while the patient in which thepacemaker is implanted is in a hospital or within a physician's office.With such systems, only very limited information, if any, can be storedby the pacemaker for subsequent transmission to the external programmer.

U.S. Pat. No. 5,431,691 to Snell et al. entitled “Method and System forRecording and Displaying a Sequential Series of Pacing Events”, however,provides a system employing a pacemaker and an external programmerwherein the pacemaker continuously records diagnostic data pertaining tothe condition of the heart of the patient for subsequent transmission tothe external programmer. The data is stored within circular bufferswithin the pacemaker configured to ensure that, if the buffers becomefull, newly recorded data overwrites the oldest previously recordeddata. The recorded data is ultimately transmitted to the externalprogrammer which is configured to provide a wide variety of differentdisplays of the data to assist the physician in analyzing the conditionof the heart and rendering appropriate diagnoses. Hence a significantimprovement is achieved over previous systems that were not capable ofstoring diagnostic data for subsequent processing and display but wereinstead only capable of displaying information pertaining to the currentcondition of the heart. U.S. Pat. No. 5,431,691 to Snell et al. isincorporated by reference herein.

The system of Snell et al. processes and records the diagnostic data inan “event record” format which allows the data to be efficiently stored,accessed and displayed. Specific types of diagnostic data processed bythe system of Snell et al. are listed in TABLE I.

TABLE I EVENT NAME EVENT TYPE AV A-pulse followed by a V-pulse ARA-pulse followed by an R-wave PVE Premature ventricular event PV P-wavefollowed by a V-pulse PR P-wave followed by an R-wave P @ MTR-V P-waveat maximum tracking rate followed by a V-pulse P @ MTR-R P-wave atmaximum tracking rate followed by a R-wave MAGNET Magnet placed over theimplanted device-either singly or in combination with an externaltelemetry system

As can be seen from TABLE I, the events processed by the system of theSnell et al. patent are primarily events sensed within the heart of thepatient. Event records containing information pertaining to those eventsare recorded within the pacemaker for subsequent transmission to theexternal programmer for display thereon in a variety of formatsincluding event record displays, event bar graphs, rate bar graphs, ratetime graphs, and event time graphs, each under the control of thephysician operating the external programmer. More specifically, theevent record display presents the various detected events of TABLE I andthe corresponding pacing rate with respect to the time of the occurrenceof the event. For periods of time while then pacemaker is in adual-chamber mode (such as DDD, DDI etc.), the events presented includePV, PR, AV (or V when the mode is VDDR or VDD), AR and PVC (prematureventricular contraction). For periods of time while the pacemaker is ina single-chamber mode (such as VVI, AAI etc.), the events are presentedmerely as paced or sensed. The event bar graph presents a histogram ofdifferent event types listing the total number of counts of each eventtype for a selected period of time. The event time graph presentshistograms of event types vs. time of event occurrence. The rate bargraph presents histograms of sensed and paced events vs. their rate. Therate time graph presents histograms of rates vs. times. Furtherinformation regarding the different displays may be found in the Snellet al. patent.

As can be appreciated a wide range of useful information, particularlydirected to events sensed within the heart, is thereby provided toassist the physician in rendering a diagnosis as to any arrhythmia orother condition the patient may exhibit or to assist the physician inmaking choices as to adjusting various parameters by which the pacemakermonitors and paces the heart. The information is displayed in a varietyof convenient graphical formats to help the physician visualize theinformation quickly and easily to facilitate prompt and accuratediagnoses.

Although the system of the Snell et al. patent represents a significantimprovement over previous systems, room for further improvement remains.In particular, it would be desirable to provide a system capable ofrecording and displaying further diagnostic data pertaining to events inaddition to those which are listed in TABLE I including, for example,diagnostic data pertaining to: events detected within the heart duringrefractory periods following stimulation pulses; operational eventstriggered within the pacemaker as a result of the condition of thepatient (such as an automode switching event); and operational eventstriggered within the pacemaker as a result of the condition of thepacemaker itself (such as battery tests or lead fault detection tests).It is to these ends that aspects of the invention are primarilydirected.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a system is provided fordetecting and displaying information received from an implantablemedical device capable of generating a stimulation signal within tissueconnected to the implantable medical device and capable of sensingelectrical events occurring within the tissue. The system comprisesmeans for receiving signals from the implantable medical devicerepresentative of events detected during a refractory period followinggeneration of a stimulation signal and means for graphically displayingicons representative of the events detected during the refractoryperiod.

In one specific example, the implantable medical device is a pacemakerand the system for detecting and displaying information is an externalprogrammer device separate from the pacemaker. The events detectedduring the refractory period include the detection of: a) a P-waveduring a relative Post-Ventricular Atrial Refractory Period (PVARP) notfollowed by a ventricular pulse; b) an R-wave during a relativeVentricular Refractory Period; or c) a P-wave during an AtrialRefractory Period during an AV/PV interval. The means for graphicallydisplaying the detected events is a computer display screen or acomputer print-out device.

In accordance with another aspect of the invention, a system is providedfor detecting and displaying information received from an implantablemedical device capable of being programmed by signals received from aremote programming device. The system comprises means for receivingsignals from the implantable medical device representative ofprogramming operations triggered within the implantable medical deviceby the signals received from the remote programming device and means forgraphically displaying icons representative of the programmingoperations triggered within the implantable medical device.

In one specific example, wherein the implantable medical device includesa pacemaker, the programming operations triggered within the pacemakerare selected from a group consisting of pacemaker mode selection, heartbase rate selection, heart rest rate selection, maximum pacemakertracking rate selection, maximum pacemaker sensing rate selection andpacemaker rate responsive AV/PV delay selection. The remote programmingdevice may be a magnet operated by a physician or may be part of aprogrammer unit operated by a physician.

In accordance with yet another aspect of the invention, a system isprovided for detecting and displaying information received from animplantable medical device that is capable of triggering internaloperations based upon sensed conditions. The system comprises means forreceiving signals from the implantable medical device representative ofoperations triggered by the implantable medical device in response toconditions sensed within the implantable medical device and means forgraphically displaying icons representative of the operations triggeredwithin the implantable medical device.

In one example, wherein the implantable medical device includes apacemaker, the pacemaker is capable of sensing conditions of the heartof a patient in which the pacemaker is implanted. The aforementionedoperations are triggered based upon the sensed conditions of the heartand include operations such as automatic pacemaker mode switching (i.e.automode switching), pacemaker mediated tachycardia (PMT) detection,premature ventricular contraction (PVC) detection, and a pacemaker ratehysteresis search.

In another example, wherein the implantable medical device againincludes a pacemaker, the pacemaker is capable of sensing performanceparameters representative of its own performance. The operationstriggered within the pacemaker are triggered based upon the sensedperformance parameters and include operations such as a battery test anda lead fault detection test.

Hence, with the invention, systems are provided for graphicallydisplaying a wide variety of diagnostic information not heretoforeeasily available to the physician, to thereby assist the physician inmaking quick and informed decisions regarding, for example, thepatient's condition or the condition of the implantable medical device.

Other objects and advantages of the invention are provided as well.Method embodiments of the invention are also provided.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 shows an implantable pacemaker coupled to a heart via a pair ofelectrical leads.

FIG. 2 is a perspective view of an external programmer that may be usedfor communicating with the implantable pacemaker of FIG. 1.

FIG. 3 is block diagram of pertinent components of the externalprogrammer of FIG. 2 for use in generating and displaying enhanced eventmarkers and event control records received from the implantablepacemaker of FIG. 1.

FIG. 4 is block diagram of pertinent components of the implantablepacemaker of FIG. 1 for use in generating the enhanced event markers andevent control records for display using the external programmer of FIG.3.

FIG. 5 is an exemplary event record screen displayed by the externalprogrammer device of FIG. 2.

FIG. 6 is an exemplary pop-up display screen displayed by the externalprogrammer device of FIG. 2 providing details of an exemplaryprogramming event that had been recorded by the pacemaker of FIG. 1.

FIG. 7 is an exemplary event bar graph display screen displayed by theexternal programmer device of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to improved techniques for providing informationto a physician regarding the events detected by an implantable medicaldevice. The invention will be described primarily with reference to apacemaker used in conjunction with an external programmer device, butprinciples of the invention are applicable to other implantable medicaldevices or other external devices as well.

The Figures illustrate a pacemaker/programmer system having a pacemakerfor implantation into a patient and an external programmer forprogramming the operation of the pacemaker and for processing anddisplaying information received from the pacemaker regarding thecondition of a patient in which the pacemaker is implanted and regardingthe condition of the pacemaker itself. The information is stored withinthe pacemaker in an event record format which efficiently allows a widevariety of types of information to be stored, along with the date andtime at which the information was stored, within the pacemaker forsubsequent transmission to the external programmer. The externalprogrammer includes processing units for receiving event recordstransmitted by the pacemaker and for generating a wide variety ofgraphical displays of the information contained within the event recordsunder the control of the physician operating the external programmer.

The Snell et al. patent, incorporated by reference above, describes apredecessor pacemaker/programmer system which also operates to generate,store and process certain types of information within event records togenerate certain displays based upon the information contained withinthe event records. The pacemaker/programmer system of the presentinvention operates to generate, store and process many additional typesof information within event records to generate enhanced displays basedupon the information contained within the event records. In thefollowing descriptions, for the sake of clarity in describing pertinentfeatures of the enhanced pacemaker/programmer system of the presentinvention, many details of the operation of the overallpacemaker/programmer system provided in the Snell et al. patent are notrepeat herein. Additional operational details pertaining to either thepacemaker, programmer or both may be found in the following patents,each of which is also incorporated by reference herein: U.S. Pat. No.4,940,052 entitled “Microprocessor controlled rate-responsive pacemakerhaving automatic rate response threshold adjustment”; U.S. Pat. No.4,809,697 entitled “Interactive Programming And Diagnostic System ForUse With Implantable Pacemaker”; U.S. Pat. No. 4,791,936 entitled“Apparatus For Interpreting And Displaying Cardiac Events Of A HeartConnected To A Cardiac Pacing Means”; U.S. Pat. No. 5,309,919 entitled“Method And System For Recording, Reporting, And Displaying TheDistribution Of Pacing Events Over Time And For Using Same To OptimizeProgramming”; U.S. Pat. No. 4,944,299 entitled “High Speed DigitalTelemetry System For Implantable Device”; U.S. Pat. No. 5,292,341entitled “Method And System For Determining And Automatically AdjustingThe Sensor Parameters Of A Rate-Responsive Pacemaker”; U.S. Pat. No.5,423,867 entitled “Rate-Responsive Pacemaker Having Automatic SensorThreshold With Programmable Offset”; and U.S. Pat. No. 4,944,298entitled “Atrial Rate Based Programmable Pacemaker With Automatic ModeSwitching Means”.

FIG. 1 illustrates an implantable pacemaker 10 coupled to a heart 12 byway of a ventricular lead 14 and an atrial lead 16. Ventricular lead 14includes an electrode 18 positioned in the right ventricle 20 of theheart and atrial lead includes an electrode 22 positioned in the rightatrium 24 of the heart.

Various internal components of the pacemaker operate to sense theelectrical activity of the heart, such as the presence of P-waves andR-waves, using electrodes 18 and 22 and to selectively stimulate theheart in response to events sensed within the heart by conductingelectrical stimulation pulses to the heart using the electrodes. Thepacemaker may be configured to operate in either a single-chamber modeor a dual-chamber mode. Certain of the events sensed within the heartare recorded by internal components of the pacemaker within eventrecords for subsequent transmission to an external programmer (FIG. 2)for display thereon in a graphical format. TABLE II provides a list ofsensed events stored in pacemaker 10 of FIG. 1 using event records whilethe pacemaker is operating in the dual-chamber mode. Notably, the eventslisted in TABLE II include three events P_(REF) detected, R_(REF)detected and P_(AV) detected occurring during refractory periodsfollowing the generation of stimulation signals.

TABLE II SENSED EVENT NAME SENSED EVENT TYPE AV A-Pulse Followed By AV-Pulse Detected AR A-Pulse Followed By An R-Wave Detected PVE PrematureVentricular Event Detected PV P-Wave Followed By A V-Pulse Detected PRP-Wave Followed By An R-Wave Detected P @ P-Wave At Maximum TrackingRate Followed By A V-Pulse MTR-V Detected P@ P-Wave At Maximum TrackingRate Followed By A R-Wave MTR-R Detected P_(REF) P-Wave Detected DuringA Relative Post-Ventricular Atrial Refractory Period (PVARP) NotFollowed By A Ventricular Pulse R_(REF) R-Wave Detected During ARelative Ventricular Refractory Period P_(AV) P-Wave Detected During AnAtrial Refractory Period During An AV/PV Interval P_(REF)R P-Wave InPVARP Followed By Sensed Inhibiting R-Wave ActAV Activity Sensor DrivenAtrial Pulse Followed By A Ventricular Pulse ActAV Activity SensorDriven Atrial Pulse Followed By Inhibiting R-Wave

For periods of time when the pacemaker is operating in thesingle-chamber mode, the pacemaker stores paced, sensed, P_(REF) andR_(REF) events, rather than all of the events of TABLE II.

Other internal components of pacemaker 10 of FIG. 1 operate to receiveprogramming signals from an external programmer (FIG. 2) and to modifythe operation of the pacemaker in accordance with the programmingsignals. Each time the pacemaker receives programming signals, thepacemaker records a record of the corresponding “programming event” asan event record for subsequent transmission to the external programmerfor display thereon in a graphical format. TABLE III provides a list ofprogramming events stored by the pacemaker 10 of FIG. 1.

TABLE III PROGRAMMING EVENT NAME PROGRAMMING EVENT TYPE Mode PacemakerMode Programmed Base Rate Heart Base Rate Programmed Rest Rate HeartRest Rate Programmed Maximum Maximum Pacemaker Tracking Rate ProgrammedTracking Rate Maximum Maximum Pacemaker Sensor Rate Programmed SensorRate Rate Rate Responsive AV/PV Delay Programmed Responsive AV/PV Delay

Still other internal components operate to automatically triggerpacemaker operations based upon the condition of the patient as sensedby the pacemaker. Such “patient condition-triggered events” are alsostored within event records for subsequent transmission to, and displayon, the external programmer. TABLE IV provides a list of all patientcondition-triggered events stored using event records by pacemaker 10.

TABLE IV PATIENT- CONDITION TRIGGERED PATIENT-CONDITION TRIGGERED EVENTNAME EVENT TYPE Auto-mode Pacemaker Mode Automatically SwitchedSwitching PMT Detection Pacemaker Mediated Tachycardia (PMT) DetectedPVC Detection Premature Ventricular Contraction (PVC) Detected Rate RateHysteresis Search Performed Hysteresis

Still other internal components operate to automatically triggerpacemaker operations based upon the condition of the pacemaker itself,such as a battery test operation triggered in response to the detectionof a low battery voltage. A record of such “pacemakercondition-triggered events” are also stored within event records. TABLEV provides a list of all patient condition-triggered events stored usingevent records by pacemaker 10.

TABLE V PACEMAKER- CONDITION TRIGGERED PACEMAKER-CONDITION TRIGGEREDEVENT NAME EVENT TYPE Battery Test Battery Voltage Test Performed VARIOTest Minimum Capture Test Performed Diagnostic Diagnostic Data SuspendedData Suspension Lead Lead Fault Detection Test Performed Supervision RRTTest Recommended Replacement Time (RRT) Battery Test Performed

Thus TABLES II-V list exemplary events stored by the pacemaker of thepresently-described exemplary embodiment of the invention within eventrecords. In other embodiments, not all of the events listed in theTABLES may be recorded. In still other embodiments, additional eventsmay also be recorded. As can be appreciated, a wide range of variationsare permissible within the scope of the invention.

As noted, the various event records are stored within the pacemaker forsubsequent transmission to, and display using, the programmer (FIG. 2)within a graphical display format. Alternatively, if the externalprogrammer is currently in communication with the pacemaker, the eventrecords may be immediately transmitted to the programmer as they arerecorded.

The specific format with which the different types of events are storedand otherwise processed differ somewhat depending upon the type ofevent. In particular, the sensed events listed in TABLE II may be storedin a different format from the various operational events listed inTables III-V. The format for storing the operational events of TABLEIII-V is referred to herein as an “event control records”. As will bedescribed below, event control records are handled somewhat differentlyduring the generation of some of the displays presented by the externalprogrammer.

FIG. 2 illustrates an external programmer 100 configured for receivingthe aforementioned event records from pacemaker 10 (FIG. 1) and forgenerating graphical displays or printouts of the event records.Programmer 100 includes a printer 102 for printing out a graphicalrepresentation of the information contained within the event records anda display screen 104 for displaying the graphical representation.Generation of the graphic displays is subject to the control of aphysician or other user operating the external programmer. To this end,external programmer 100 presents various menus on display screen 104 foruse in controlling operation of the programmer to program pacemaker 10(FIG. 1) to perform any of the functions listed above in TABLE III.Various menus are also presented on display screen 104 for use incontrolling operation of the programmer to generate displays on displayscreen 104 of information received from the pacemaker including theaforementioned graphical representations of the event recordsrepresentative of the events listed above in TABLES II-V. Programmer 100receives menu selections from the physician through a touch screen 108which overlays display screen 104. Actual programming of the pacemakeris achieved using a telemetry head 106 which, in use, is placed isproximity to the pacemaker.

With reference to FIGS. 3 and 4, internal components of pacemaker 10 andprogrammer 100 that are pertinent to the processing of event recordswithin the pacemaker and to the generation of event record displaysusing the external programmer will now be described. Components ofprogrammer 100 are shown in FIG. 3. Components of pacemaker 10 are shownin FIG. 4. Referring first to FIG. 3, a controller 110 of programmer 100controls graphic display 104 to display the aforementioned menus fromwhich the physician may select, among other options, to program theoperation of the pacemaker or to generate graphical displays of theevent records previously recorded by the pacemaker.

Assuming first that the physician chooses to program the pacemaker, aprogram function selection unit 112 controls graphic device 104 todisplay a list of the programming options corresponding to theprogramming events listed in TABLE III, i.e. the graphic device displaysa list of the following programming options: Mode, Base Rate, Rest Rate,maximum Tracking Rate, Maximum Sensing Rate, and Rate Responsive AV/PVDelay. (Further information regarding these programming options may befound in the above-referenced patents.) The physician selects one ormore of the programming options from the list then enters any pertinentparameters, such as the applicable pacemaker mode, rate value or delayvalue, on one or more display screens (not separately shown) presentedby programmed function selection unit 112 using graphical display 104. Acommand transmitter unit 114 of telemetry head 106 transmits theappropriate command signals to pacemaker 10 to program the pacemaker inthe selected manner.

Referring to FIG. 4, the programming signals transmitted by programmer100 are received by a command receiver unit 116. A controller 118operates in response to the received commands to program the appropriatepacemaker functional units (not shown) to perform the selectedoperations in response to the programming signals. Additionally, theprogramming signals are forwarded by command receiver unit 116 to aprogrammed function storage unit 120 which stores information pertainingto the received programming command as an event control record (alongwith the date and time that the command was received) in an event datastorage unit 122 to thereby maintain a record of the receipt of theprogramming signal or subsequent access. Event data storage unit 122 maybe a circular buffer configured as described in the Snell et al. patent.

The event data storage unit additionally stores a wide variety of otherpacemaker event information including event records corresponding to anyof the other events listed within TABLES III-V. To this end, pacemaker10additionally includes pacemaker condition-triggered function unit 123,a patient condition-triggered function unit 125 and a sensed eventdetection unit 127, each of which operates continuously andautomatically within the pacemaker (subject to the overall control ofcontroller 118) to detect particular events, trigger responsiveoperations and record information pertaining to the detected eventswithin event data storage unit 122. The specific information to berecorded along with each event varies depending upon the particularevent. For example, for the sensed events of TABLE II, the rate at whichthe event was detected is stored along with an identification of thetype of sensed event. For the events of Tables III-V, the correspondingevent control record that is stored includes an identification of thetype of event and any additional pertinent information. For example, foran automode switching event, the event control records storedadditionally contains an identification of the previous pacemaker modeand the new pacemaker mode. For a battery test event, the event controlrecord additionally stores an indication of whether the battery failedthe test.

Now the purpose of the various functional units of the pacemaker of FIG.4 will be described. Pacemaker condition-triggered function unit 123continuously monitors the operation of other units of the pacemaker,such as the pacemaker battery (not shown) and triggers appropriateoperations in response thereto. More specifically, pacemakercondition-triggered function unit 123 triggers a battery test, a VARIOtest, a lead supervision test and an RRT criteria test. The battery testis periodically performed to determine if the battery has sufficientpower by, for example, determining if the battery voltage has fallenbelow a predetermined minimum threshold and, if so, appropriate warningsignals are generated. Also, the pacemaker may modify its ownoperations, perhaps to suspend further diagnostic data acquisition tosave battery power. The VARIO test is a minimum capture test performedto determine the minimum voltage of a stimulation pulses sufficient tobe captured and responded to by the heart. Typically, the voltage levelfor stimulation pulses is then set based upon the minimum capturethreshold to ensure that a minimum amount of energy is used in eachstimulation pulse while still ensuring adequate capture of the pulse.The lead fault detection test (also referred to a Lead Supervision test)is periodically performed to test the integrity of the electrical leads(FIG. 1) perhaps by sensing the impedance thereof. The recommendedreplacement time (RRT) test is periodically performed to determine ifthe battery, or other power source of the pacemaker, should be replacedand, if so, appropriate warning signals are generated. The RRT testdiffers from the previously-described battery test in that a moresophisticated set of tests are performed. Additionally, pacemakercondition-triggered function unit 123 may selectively suspend thefurther acquisition of diagnostic data. This is typically done if thebattery begins to lose power. By suspending diagnostic data acquisition,a greater amount of remaining battery power is thereby preserved forsensing and pacing the heart.

Each time an operation is triggered by pacemaker condition-triggeredfunction unit 123, the unit also operates to store an event controlrecord within data storage unit 122 representative of the triggeredevent. Accordingly, each of the events listed in TABLE III, above, maybe recorded within the data storage unit.

Patient condition-triggered function unit 125 continuously monitors thestatus of the patient's heart via an electrical sensor unit 129connected to leads 14 and 16 (FIG. 1) and triggers appropriateoperations in response to certain detected conditions. Morespecifically, patient condition-triggered function unit 125 triggersautomode switching, PMT detection, PVC detection and a rate hysteresisoperation. Automode switching is performed to automatically switch thepacing mode of the heart to, for example, switch from a dual mode to asingle chamber mode. PMT detection is performed continuously to detect apacemaker mediated tachycardia such as an endless loop tachycardia, atracking atrial fibrillation. PMT is also referred to as pacemakerreentry tachycardia, circus tachycardia or endless loop tachycardia. IfPMT is detected, appropriate responsive therapy is automaticallyperformed by the pacemaker in an attempt to terminate the PMT. Forexample, atrial sensing may be terminated via an automode switchingoperation. PVC detection is performed continuously to detect prematureventricular contractions (i.e. ventricular contractions occurring duringa pre-defined refractory period). The physician may elect to shorten therefractory period to ensure that PVC pulses are properly sensed. Propersensing of PVC's may be helpful in eliminating or preventing PMT's. Therate hysteresis search is performed periodically to set the hysteresisescape rate. The hysteresis escape rate is typically set to a value lessthan the base rate to inhibit pulse generation in some circumstances toallow the heart further time to generate its own pulse.

Each time an operation is triggered by patient condition-triggeredfunction unit 125, the unit also operates to store an event controlrecord within data storage unit 122 representative of the triggeredevent. Accordingly, each of the events listed in TABLE IV, above, may berecorded within the data storage unit.

Sensed event detection unit 127 continuously monitors the signalsreceived from the patient's heart to detect selected events and recordspertinent information pertaining to the events within the data storageunit. More specifically, sensed event detection unit 127 detects each ofthe events listed in TABLE II. The last three events, namely P_(REF),R_(REF) and P_(AV), are events occurring during a refractory periodfollowing generation of a stimulation pulse. Knowledge of theserefractory events is helpful to the physician in setting refractoryperiods and the like.

Thus while pacemaker 10 of FIG. 1 is in operation, it continuouslymonitors various aspect of its condition and the condition of thepatient in which it is implanted and stores appropriate diagnosticinformation as event records in event data storage unit 122.Additionally, as noted above, the pacemaker may receive programmingcommands which are also stored in the data storage unit.

Ultimately, the physician may wish to display diagnostic informationpertaining to any of the events previously recorded. Such may bedesirable during a follow-up session with the patient in which thepacemaker is implanted. To display the diagnostic information, thephysician then selects for the display of recorded events (by usingappropriate menus not separately shown herein displayed by graphicdevice 104 of FIG. 3). Controller 110 forwards appropriate event recordretrieval commands to pacemaker 10 (FIG. 4) via command transmitter unit114 of telemetry head 106. The retrieval commands are received bycommand receiver unit 116 of the pacemaker of FIG. 4 and forwarded to anevent record access unit 131 which retrieves all stored event recordsfrom event data storage unit 122 for transmission to the programmer viaa data transmitter unit 130. The event records are received by a datareceiver unit 132 of telemetry head 106 of the programmer of FIG. 3 andforwarded to an event display generation unit 134. The event displaygeneration unit operates to display a representation of the eventrecords using either graphic device 104, printer 102, or both.Additionally, the event display generation unit may trigger anannunciator 136 to generate an audible sound upon the display of certainevent records to help direct the physician's attention to the display.

A variety of graphical displays of information contained within theevent records may be generated under control of the physician. In thepresently described exemplary embodiment, the following graphicaldisplays of information contained within the event records may bedisplayed under the control of the physician: event record displays,event bar graphs, rate bar graphs, rate time graphs, and event timegraphs. The event record display presents the various detected events ofTables II-V and the corresponding pacing rate with respect to the timeof the occurrence of the event. Briefly, for periods of time while thepacemaker is in a dual-chamber mode (such as DDD, DDI etc.), the eventspresented include PV, PR, AV (or V when the mode is VDDR or VDD), AR andPVC (premature ventricular contraction). For periods of time while thepacemaker is in a single-chamber mode (such as VVI, AAI etc.), theevents are presented merely as paced or sensed. The event bar graphpresents a histogram of different event types listing the percentage oftime of each event relative to the total event time. The event timegraph presents histograms of event types vs time of event occurrence.The rate bar graph presents histograms of sensed and paced events vs.their rate. The rate time graph presents histograms of rates vs times.In other embodiments, more or fewer displays may be generated. Detailsof the manner by which the various event record displays are generatedare provided in the Snell et al. patent. Accordingly, the followingdescriptions will be directed primarily to the portions of selecteddisplays containing additional information not provided by the displayscreens of the Snell et al. patent.

FIG. 5 illustrates an exemplary event record display screen 140 forevents recorded during a period of time when the pacemaker was in adual-chamber mode. The event record display screen includes a graphicaldisplay 142 of recorded events shown using various graphical iconsdistributed along a horizontal time axis and a vertical rate axis. Theevents displayed may include any of the events listed in the TABLESabove. The sensed events of TABLE II are represented each by a uniqueicon positioned along the time axis of the graphic display at the timeat which the event was sensed as recorded within the corresponding eventrecord and positioned along the rate axis at a location representativeof the rate at which the event was sensed. In the example of FIG. 5,rates are scaled between 30 and 190 pulses per minute (ppm). Legend 144provides a summary of the unique graphical icons presented in display142 such as: an A for an AR event; a P for PR event; a square black boxwith a reverse video ‘A’ for an AV event; a square black box with areverse video ‘P’ for a PV event; a ‘★’ for a PVE event; a white squarebox for a P_(AV) event; an upside down black triangle for P_(REF) event;a black triangle for R_(REF) event; etc. All other events (i.e. theevents listed in Tables III-V) are identified as ‘event markers’ and aregraphically represented by sequential arabic numerals each within acircle, such as a 1 in a circle. The event markers themselves aredisplayed along a top portion 145 so graphical display 142 at a pointalong the time-axis corresponding to the time at which the event wasrecorded by the pacemaker. The event markers, however, are not scaledalong the vertical rate axis. For an automode switching event, inaddition to providing an arabic numeral in a circle, the previous andsubsequent pacemaker modes are also displayed (e.g. DDD v. DDI).

For data collected during a period of time when the pacemaker was in asingle-chamber mode, the event record display shows a solid black squarebox with a reverse video ‘s’ for a paced event, an ‘s’ for a sensedevent, an upside down black triangle for a P_(REF) event and a blacktriangle for an R_(REF) event

In the dual-chamber example of FIG. 5, a variety of AV, PV, AR and PRevents are shown, along with four refractory period events 147: oneP_(AV) event followed by two P_(REF) events and a single R_(REF) event.The latter R_(REF) event is followed by a star icon indicated the firstsubsequent sensed event.

The event record display also provides a selectable time scale list 150to allow the physician to select the time scale over which data is to bedisplayed within graphical display 142. As shown, exemplary time scalesinclude fifteen seconds, one minute, five minutes, fifteen minutes andthirty minutes. Although not shown, additional time scales include onehours, two hours, five hours, twelve hours, thirty hours, sixty hours,one hundred twenty hours, one week, two weeks, four weeks, eight weeks,sixteen weeks, thirty weeks, and fifty-two weeks. Depending upon thetime scale, the event record display may not be able to show allindividual events. If so, the event record display presents a compresseddisplay with time slots providing the maximum, minimum and average ratesof the events within the time slots.

The event record display also provides a ZOOM button 152 which, uponselection, causes the external programmer to selectively display only aportion of the previous event record display. At that time, the ZOOMbutton is replaced with an UN-ZOOM button to allow for a return to theprevious display. Furthermore, the event record display includes a timebar 154 which graphically indicates the portion of the total amount ofevent record data received from the pacemaker that is currentlydisplayed. In the example of FIG. 5, only about one third of the totalevent record data retrieved from the pacemaker is displayed. Selectionof one of the arrow buttons 156 and 158 causes the graphical display tobe scrolled to the left or right, respectively, to display otherportions of the event record data received from the pacemaker.Additionally, a vertical line 160 is displayed to provide a marker toassist the physician in scrolling or otherwise examining data. Althoughnot shown, still other buttons may be presented on the displayincluding, for example, a PRINT button or a CANCEL button.

A selectable event marker list 162 displays a list of the displayedevent markers by number. Upon selection of one the events listed in theevent marker list, programmer 100 (FIG. 3) generates a pop-up displayproviding pertinent information pertaining to the selected event marker.

FIG. 6 provides an example of a pop-up display providing informationpertaining to one event marker, specifically a “base rate change”programming event recorded by the pacemaker (and identified within FIG.5 as event marker ‘1’). As can be seen from FIG. 6, the pop-up displayprovides a textual description of the base rate programming operationincluding the new base rate as well as the date and time at which thebase rate change occurred. Selection of a CONTINUE button 148 within thepop-op display causes the external programmer to redisplay the eventrecord display of FIG. 5 to allow for selection of another event markerfor generation of another pop-up display or for selection of any otherappropriate function.

For each different event marker, different information may be providedwithin the pop-up display. Generally speaking, all pertinent informationstored as part of the event control record is displayed. Thus, forexample, in the pop-up display generated from a battery test eventmarker, the pop-up display indicates whether the battery failed the testand additionally displays the date and time. Additional diagnosticinformation may be presented as well. For example, for a pop-up displaygenerated from an RRT. test event marker wherein the recommendedreplacement has been reached, the following information is presentedalong with the date and time of the RRT:

“Pulse generator has reached RRT for the following possible reasons:

1. Battery is RRT;

2. Battery is near RRT.

3. RRT Triggered because of high output pacing

4. RRT was possibly triggered by applied defibrillator/discharge

5. RRT could have been triggered by implantable defibrillator.”

Referring to FIG. 7, an exemplary event bar graph display 170 is shownhaving a bar graph 172 providing a set of bars each separatelycorresponding to one of the sensed events listed in TABLE II, namely PV,PR, AV, AR, PVE and the three refractory period events P_(REF), R_(REF)and P_(AV). The bars are distributed along a vertical axis of the bargraph and extend upwardly along a vertical axis representative of“Percentage of Total Time”. Each of the bars for the PV, PR, AV, ARevents are sub-divided into different sections. More specifically, a PV174 bar is split into three sections to show the relative percentages ofdata collected either @MTR-V, above the base rate or below the baserate. A PR bar 176 is split into two sections to show the relativepercentages of data collected either above the base rate or below thebase rate. An AV bar 178 is split into three sections to show therelative percentages of data either sensor driven, collected above thebase rate or collected below the base rate. An AR bar 180 is also splitinto three sections to show the relative percentages of data eithersensor driven, collected above the base rate or collected below the baserate. The remaining bars: a PVE bar 182, a P_(REF) bar 184, a R_(REF)bar 186, and a P_(AV) bar 188 are not individually sub-divided. An eventcount table 190 is also provided which lists the actual numerical countsof each category of event shown in the event bar graph. For eventrecords recorded during periods of time when the pacemaker was in asingle-chamber mode, the event histogram includes only histogram barsfor sensed, paced, P_(REF) and R_(REF).

Thus a few exemplary displays of the event record data havebeen-specifically illustrated. Additionally, a variety of other displaysare generated by the exemplary embodiment of the invention including theaforementioned event bar graphs, rate bar graphs, rate time graphs, andevent time graphs, which each provide different graphicalrepresentations of the sensed events of TABLE II. Additionally detailsregarding the characteristics of those displays are provided in theSnell et al. patent. Of course, it should be understood, that in theexemplary embodiment herein described, each of those displays ismodified as appropriate to additionally incorporate the refractoryperiod events P_(REF), R_(REF) and P_(AV). Also, it should be noted thata wide variety of other types of displays of the event records mayalternatively be generated in accordance with the principles of theinvention. For example, a graphical display may be generated that merelyprovides a list of all of the event records along with the date and timeat which the events were recorded, perhaps arranged in chronologicalorder.

Eventually, the physician terminates the presentation of graphicalrepresentations of the event records by selecting an appropriate menuoption, such as a CANCEL menu option (not shown), and can thereafterselect other programmer operations.

What has been described are systems for generating, storing, processingand graphically displaying a wide variety of information pertaining toevents detected by a pacemaker. The various functional components of theexemplary system may be implemented using any appropriate technologyincluding, for example, microprocessors running software programs orapplication specific integrated circuits (ASIC'S) executing hard-wiredlogic operations. Although described with respect to a pacemaker used inconjunction with an external programmer, aspects of the invention areapplicable to other system, such as systems employing other implantablemedical devices or systems employing other types of external interfacesfor use with the implantable device. The exemplary embodiments of theinvention described herein are merely illustrative of the invention andshould not be construed as limiting the scope of the invention.

What is claimed is:
 1. A system for detecting and displaying informationreceived from an implantable medical device that is capable oftriggering operating changes based upon sensed conditions, said systemcomprising: means for receiving signals from the implantable medicaldevice representative of the operating changes triggered within theimplantable medical device; and means for graphically displaying iconsrepresentative of the operating changes triggered within the implantablemedical device.
 2. The system of claim 1, wherein the operating changesrepresented are selected from a group consisting of pacemaker auto-modeswitching, pacemaker mediated tachycardia (PMT) detection, prematureventricular contraction (PVC) detection, and a pacemaker rate hysteresissearch.
 3. The system of claim 1, wherein the operating changes areselected from a group consisting of a battery test, a minimum capturetest, the suspension of the acquisition of diagnostic data, a lead faultdetection test, and a recommended battery replacement time test.
 4. Thesystem of claim 1, wherein the means for graphically displaying theicons comprises a computer display screen.
 5. The system of claim 1,wherein the means for graphically displaying the icons comprises acomputer print-out device.
 6. A method for detecting and displayinginformation using an implantable medical device and an external displaydevice, said method comprising the steps of: sensing conditions usingthe implantable medical device; triggering operating changes within theimplantable medical device in response to the sensed conditions;transmitting signals, from the implantable medical device to theexternal display device, representative of operating changes triggeredwithin the implantable medical device in response to the sensedconditions; receiving the transmitted signals at the external displaydevice; and graphically displaying icons on the external display devicerepresentative of the operating changes that had been triggered withinthe implantable medical device.
 7. The method of claim 6, wherein thestep of sensing conditions using the implantable medical device includesthe step of sensing conditions within a patient in which the medicaldevice is implanted.
 8. The method of claim 7, wherein the implantablemedical device includes a pacemaker and wherein the step of triggeringoperating changes includes the step of selecting from a group consistingof performing pacemaker auto-mode switching, detecting pacemakermediated tachycardia (PMT), detecting premature ventricular contraction(PVC), and performing a pacemaker rate hysteresis search.
 9. The methodof claim 6, wherein the step of sensing conditions using the implantablemedical device includes the step of sensing parameters representative ofits own performance.
 10. The method of claim 9, wherein the implantablemedical device includes a pacemaker and wherein the step of triggeringoperating changes within the implantable medical device includes thestep of selecting from a group consisting of performing a battery test,performing a minimum capture test, suspending the acquisition ofdiagnostic data, performing a lead fault detection test, and performinga recommended battery replacement time test.
 11. A system for detectingand displaying information, comprising: an implantable medical devicethat is operative to trigger operating changes based upon sensedconditions and to generate corresponding signals representative of theoperating changes; and an external display device that is operative toreceive the signals from the implantable medical device, wherein theexternal display device is further operative to process the signals andto graphically display icons representative of the operating changes.12. The system of claim 11, the implantable medical device is capable ofsensing conditions of a patient in which the medical device is implantedand wherein the operating changes are triggered based upon theconditions of the patient.
 13. The system of claim 12, wherein theimplantable medical device comprises a pacemaker and wherein theoperating changes represented are selected from a group consisting ofpacemaker auto-mode switching, pacemaker mediated tachycardia (PMT)detection, premature ventricular contraction (PVC) detection, and apacemaker rate hysteresis search.
 14. The system of claim 11, whereinthe implantable medical device is capable of sensing performanceparameters representative of its own performance and wherein theoperating changes are triggered based upon the sensed performanceparameters.
 15. The system of claim 14, wherein the implantable medicaldevice comprises a pacemaker and wherein the operating changes areselected from a group consisting of a battery test, a minimum capturetest, the suspension of the acquisition of diagnostic data, a lead faultdetection test, and a recommended battery replacement time test.
 16. Thesystem of claim 11, wherein the external display device comprises acomputer display screen.
 17. The system of claim 11, wherein theexternal display device comprises a